Device and method for adapting the size of an ion beam spot in the domain of tumor irradiation

ABSTRACT

The invention relates to an apparatus and to a method for adapting the size of an ion beam spot in tumor irradiation. For that purpose, the apparatus has a raster scanning device composed of raster scanning magnets ( 20 ) for raster scanning the ion beam ( 19 ). In addition, the apparatus comprises quadrupole magnets ( 10 ) determining the size of the ion beam spot, which quadrupole magnets ( 10 ) are arranged directly in front of the raster scanning magnets ( 20 ), and finally two magnet power supply units ( 18 ) for the quadrupole doublet of the quadrupole magnets ( 10 ) determining the size of the ion beam spot, the apparatus having a control loop for obtaining current correction values, by comparing desired and actual values of the prevailing dimension of the beam, for two magnet power supply units ( 18 ) of the quadrupole doublet arranged directly in front of the raster scanning magnets ( 20 ), for defined homogenization and/or for defined variation of the size of the ion beam spot.

This application is 371 of PCT/EP01/13571 filed on Nov. 21, 2001, pushedon May 30, 2002 under publication number WO 02/41948 A1 which claimspriority benefits from German patent application number DE 100 57 824.1filed Nov. 21, 2000.

The invention relates to an apparatus for adapting the size of an ionbeam spot in tumour irradiation according to the precharacterisingclause of claim 1 and to a method for adapting the size of an ion beamspot according to the independent method claim.

An apparatus corresponding to the precharacterising clause of claim 1and an intensity-controlled raster scanning process are known from thearticle by Th. Haberer, W. Becher, D. Schardt and G. Kraft “Magneticscanning system for heavy ion therapy” published in Nuclear Instrumentsand Methods in Physics Research, A330 (1993), pages 206-305. There arefurther known from Patent Application DE 198 35 209.3, “Apparatus andmethod for controlling an irradiation device”, an apparatus and a methodbased on a control system that renders possible reliable scanning of atumour volume of a patient by means of a raster scanning process. Thatapparatus has the disadvantage, however, that it is not possible withouta great deal of effort to adjust the size of the ion beam spot duringand between the irradiation points and therefore the size of the ionbeam spot remains the same width during every section through the tumourvolume and thus, in particular, does not permit sharp outlines in theedge region.

The object of further developing that control system is to obtain anincrease in the geometrical precision of the dose application and amarked enhancement of the robustness of the process towards beamposition variations, especially also in view of the future use ofrotatable beam guides (gantries) with integrated raster scanningtechnology.

The magnitude of the unavoidable beam position variations which arecaused by more difficult ion-optical conditions increases in the case ofrotatable beam guides (gantries). Even if the intensity of the therapybeam varies between maximum value and minimum value by a factor of 30,the beam position variation of the therapy beam supplied by theaccelerator should and must be within a range of ±2 mm. It isaccordingly also an object of the invention to implement a preciseirradiation plan so that the dose distribution resulting from the totalirradiation deviates from the planned dose distribution by on averageless than 5%.

That object is achieved with the subject-matter of the independentclaims. Features of advantageous developments of the invention will beapparent from the dependent claims.

According to the invention, the apparatus for adapting the size of anion beam spot in tumour irradiation has a raster scanning devicecomposed of raster scanning magnets for raster scanning the ion beam. Inaddition, quadrupole magnets which determine the size of the ion beamspot are provided directly in front of the raster scanning magnets. Thequadrupole doublet of the quadrupole magnets determining the size of thebeam spot is powered according to the invention by two magnet powersupply units.

In an apparatus used hitherto, during extraction of the therapy beamfrom a suitable accelerator, such as a synchrotron, variations with timeof ion-optical parameters in the accelerator or of the subsequent beamguide can give rise to both beam position variations and variations withtime of the beam spot sizes. While the partial problem of beam positionvariations has meanwhile been solved extremely effectively, there hasnot hitherto been any method for reducing or controlling variations inthe size of the beam spot.

The aim of tumour ion-irradiation, however, is to produce particleallocations that are as exact as possible, that is to say, within thetarget volume the deviations from the planned dose distribution are tobe minimised, the beam width variations are tolerable only to a limitedextent since otherwise the geometrical pattern of the beam positions,which has been previously specified when planning the irradiation, isable to provide sufficiently exact irradiation results only for adefined range of the beam width.

For that reason, according to the invention the apparatus has a controlloop that provides current correction values, by comparing desired andactual values of the prevailing beam count, for two magnet power supplyunits of the quadrupole doublet arranged directly in front of the rasterscanning magnets and provides a defined homogenization and/or a definedvariation of the size of the beam spot during beam extraction and/orfrom measuring cycle to measuring cycle and/or from beam position tobeam position.

The solution according to the invention has the advantage that asensible ratio of beam profile width to beam position spacing can bemaintained during the irradiation, thereby providing homogeneous dosedistributions that meet the medical requirements, as shown in FIG. 2.

In order to obtain such a homogeneous beam distribution, the apparatuspreferably has real-time software for calculating the actual values ofthe ion beam width from raw detector data. In addition, the apparatushas a position-sensitive detector for detecting the ion beam width andfor producing raw detector data on the ion beam width. An advantage ofthat embodiment of the invention is that it enables very steep dosegradients to be produced at the edge of the volume being irradiated byvarying the width of the ion beam towards the edge.

The size of the beam spot is minimised towards the edge for a steep edgedrop, so that the range of that drop in dose scaled with the full widthat half maximum of the therapy beam is possible. The advantageassociated with that apparatus for regulating the size of the beam spotis that the duration of irradiation for the patient in the irradiationchamber, with the patient in an immobilised position, can be minimisedsince a large ion beam spot size can be implemented in wide regions ofthe tumour volume and it is only towards the edge that the size of theion beam spot is reduced and the beam positions are made denser per unitof area, as shown in FIG. 3, in order to achieve a more precise tracingof the edge.

The duration of an irradiation and hence also the patient throughput ofa system is reduced by the reduced density of the beam positions in thevolume of the tumour since, as the density of the beam positionsdecreases, the duration of the irradiation also decreases. Thus, areduction in the duration of the irradiation is advantageously obtainedas a result of the possibility of adjusting the size of the beam spot,since fewer beam positions at a greater spacing can be planned in theinner volume of the tumour. In order, on the other hand, to ensure anadequate quality of the particle allocations over the cross-section ofthe tumour, however, a minimum width of beam spot is required for agiven beam position spacing. That in turn is ensured by the apparatusaccording to the invention.

In a further preferred embodiment of the apparatus, it has control andread-out modules and associated data connections in order to sendinformation on the actual value of ion beam widths to a storage, controland read-out module and store the measurement data. That embodiment ofthe invention has the advantage that, by interaction of the control andread-out module with the magnet power supply units of the quadrupoledoublet of the quadrupole magnets determining the size of the ion beamspot, speedy variation of the size of the ion beam spot can be ensured.

In a further embodiment of the invention, the read-out module has anumber of free interfaces and a computing capacity by means of which thetracking of the ion beam width can be performed. The requirement of asteep and precise edge drop with minimum duration of the irradiation,which is understandable from a medicotechnological viewpoint, istherefore advantageously achieved with regard to the size of theirradiation spot, which cannot be achieved in the current state of theart because of the rigid size of the ion beam spot. With the ability totrack and to adjust the size of the beam spot and the position of thebeam spot dynamic adaptation during the irradiation of a tumour volumeis advantageously obtained, whereby the person planning the irradiationis also provided with greater flexibility in specifying the beamposition pattern, and the quality of the dose distribution can befurther enhanced.

In an alternative embodiment of the apparatus, a control system that isexpanded by one control and read-out module is provided, the additionalcontrol and read-out module being able to perform exclusively thefunction of ion beam width regulation. With that embodiment, rapidadjustment becomes possible in periods of time that are substantiallyshorter than typical accelerator cycle times.

In a further preferred embodiment of the invention, the apparatus has acontrol loop which starts from a multiwire ionization chamber withattached control and read-out module and leads to a control and read-outmodule that provides measurement data for graphical representation andactuates two magnet power supply units for horizontal and verticalfocusing of the quadrupole doublet directly in front of the rasterscanning magnet. Corrected field settings are thereby advantageouslyproduced, which improve the focusing state of the system. The control isable to ensure in an advantageous manner both the maintenance of aconstant size of ion beam spot during the scanning process and thedefined variation of the size of the ion beam spot in accordance with anirradiation planning procedure. In that control process, the informationon the variation of the beam width with time which is available from theposition measurement of the raster scanning system is combined with theability of the control system to apply to the magnet power supply unitsof magnets that influence the size of the ion beam spot, such as, forexample, quadrupole magnets, new desired values in rapid succession, sothat, from a current comparison of desired and actual value of theprevailing dimension of the beam, it is possible to calculate currentcorrection values for both magnet power supply units of a quadrupoledoublet directly in front of the raster scanning magnet.

A method for adapting the size of an ion beam spot in tumour treatmentis characterised by the following method steps:

-   -   dynamic adaptation of the size of an ion beam spot in real time        by    -   applying desired values for different ion beam spot sizes to the        quadrupole magnet determining the size of the ion beam spot        within an acceleration cycle and/or between two successive        acceleration cycles and/or between adjacent beam positions by        means of adjustable frequency,    -   obtaining current correction values, by comparing desired and        actual values of the prevailing dimension of the beam, for two        magnet power supply units of the quadrupole doublet of the        quadrupole magnets determining the size of the ion beam spot,        for defined homogenization and/or for defined variation of the        size of the ion beam spot during beam extraction and/or from        measuring cycle to measuring cycle and/or from beam position to        beam position,    -   irradiating tumour tissue with a denser ion beam position raster        and, at the same time, a smaller ion beam spot size in the edge        region than in the volume region of the tumour.

The method according to the invention thus improves the previouslydescribed raster scanning process in several respects. Owing to thepossibility of setting the size of the ion beam spot in real time, thequality of the particle allocations produced by the raster scanner canbe enhanced by actively adapting the current beam width to thespecifications of the irradiation plan by means of a control process.The geometrical density of the beam positions can thereby be reduced incomparison with the previous irradiation mode, especially sincepreviously it was necessary to have a reserve in order to compensate forthe variations in beam width which always occurred. The control processaccording to the invention, which minimises those variations, providesthe possibility of planning a smaller number of beam positions, whichleads to shorter irradiation times and a higher patient throughput.

In a preferred implementation example of the method, the beam full widthat half maximum is adapted to the ion beam position raster in such a waythat, in the case of the fine ion beam position raster in the edgeregion, a smaller beam full width at half maximum is set than in thevolume region of the tumour with a coarse ion beam position pattern. Asa result, it is advantageously possible to obtain a more precisedemarcation between tumour tissue and healthy tissue in the edge regionsince, at the same time, the beam full width at half maximum is setsmaller and therefore in a more sharply defined manner than in thevolume region of the tumour. By means of the greater beam full width athalf maximum in the volume region of the tumour with a coarse ion beampattern, the total number of beam positions per isoenergy section, thatis to say per irradiation plane, can advantageously be reduced andtherefore the irradiation treatment time can be reduced. On the otherhand, the dose gradient at the edge of the tumour tissue is very steepand thus ensures precise demarcation between tumour tissue and healthytissue.

A further preferred implementation example of the method provides thatfor every measuring cycle real-time software in a control and read-outmodule of a multiwire ionization chamber calculates the actual value ofthe ion beam width from the raw detector data of the multiwireionization chamber. In that case, a procedure is preferably carried outin which the beam full width at half maximum is varied and set frommeasuring cycle to measuring cycle, calculation of the beam full widthat half maximum being performed by collecting raw detector data of amultiwire ionization chamber. Such real-time software has sufficienttime between measuring cycle and measuring cycle and/or between adjacentbeam positions to re-calculate the appropriate setting data in anadapted form.

In a further preferred implementation example of the method, informationon the beam width is supplied to a module for storing the measurementdata and for controlling and reading-out. That module may serve, on theone hand, initially to store the raw detector data and to re-correlatethe raw detector data from beam position to beam position or frommeasuring cycle to measuring cycle.

In a further implementation example of the method, a module for storing,controlling and reading-out the actual values of the ion beam spot sizeis compared in real time with the information on the desired value ofthe ion beam spot size from an irradiation plan. Using such a module,the size of the ion beam spot not only can be detected and variedbetween measuring cycle and measuring cycle and/or between beam positionand beam position but also can be varied during and within a beamextraction. For that purpose, in a further implementation example of themethod, a correction value for magnet power supply units of thequadrupole doublet of the quadrupole magnets of a high-energy radiationguide directly in front of the raster scanner, which quadrupole magnetsdetermine the size of the ion beam spot, can be determined and setaccordingly.

If, in a further implementation example of the method, the procedure iscarried out from measuring cycle to measuring cycle, aposition-measuring system can perform correction and re-setting from oneion beam position in the irradiation plan to the next ion beam position.That re-setting is initially already specified by setting the frequencyof tracking of the ion beam in the form of a parameter of real-timesoftware that determines and executes the correction values for thequadrupole doublet. The attenuation of the ion beam width is alsoadjustable analogously to the frequency of the adaptation by means of aparameter. Finally, threshold values can be established for the ion beamwidth in respect of maximum and minimum ion beam width in order toexclude the possibility of maladjustment from the outset.

The method according to the invention and the apparatus according to theinvention are accordingly concerned with readjustment of the beam widthin real time. For that purpose, the information on the course of thebeam width with time, which is available from the position measurementof the raster scanning system, is combined with the ability of thecontrol system to apply to magnet power supply units of magnets thatinfluence the size of the ion beam spot, such as quadrupole magnets, newdesired values in rapid succession. A control loop is thereby formedwhich makes it possible for current correction values for the two magnetpower supply units of the quadrupole doublet directly in front of theraster scanning magnets to be calculated from a comparison of desiredand actual values of the prevailing dimension of the beam and thus forcorrected field settings to be produced which improve the focusing stateof an ion beam therapy system. It is thus possible for the control toprovide for a constant ion beam spot size and to be maintained morereliably during the scanning process and for defined variations of thesize of the ion beam spot to be performed in accordance with thespecifications of an irradiation plan that can be made considerably moreflexible.

FIG. 1 shows an example of an inhomogeneous dose distribution at toosmall a beam full width at half maximum.

FIG. 2 shows an example of a homogeneous dose distribution with anadequate beam full width at half maximum.

FIG. 3 shows an illustrative embodiment of a beam position distributionthat becomes possible by employing the apparatus according to theinvention.

FIG. 4 shows an embodiment of an irradiation system in which theapparatus according to the invention can be employed.

FIG. 5 shows a data flow diagram of an illustrative embodiment of theinvention.

FIG. 1 shows an example of an inhomogeneous dose distribution at toosmall a beam full width at half maximum. For that purpose, in FIG. 1 aco-ordinate system is set up in the X, Y and Z directions, the units forthe X and Y axes being millimeters and the radiation dose being plottedin the direction of the Z axis. FIG. 1 illustrates the effect on thehomogeneity of the dose distribution of a beam profile width notconforming to specifications of a radiation plan. An inhomogeneity thatis unacceptable for tumour irradiation is to be seen at the irradiationdose maxima projecting in the Z direction.

In principle, the beam profile width is too narrow in relation to thebeam position spacings or, conversely, the beam position spacings aretoo large for the set beam profile width. An essential objective of beamapplication is not achieved, therefore, namely the production of aparticle allocation that is as exact as possible, that is to say, withinthe target volume the deviations from the planned dose distribution areto be minimal, and therefore an irradiation inhomogeneity is obtainedfor the beam profile width set in FIG. 1 and the specifications of theirradiation plan cannot be met.

FIG. 2 shows an example of a homogeneous dose distribution at anadequate beam full width at half maximum. In FIG. 2, once again an X, Yand Z co-ordinate system is shown with a millimeter scale on the X and Yaxes and a dose quantity in the direction of the Z axis. In thisembodiment, a sensible ratio of beam profile width to beam positionspacing is maintained during the irradiation, with the result that ahomogeneous dose distribution that satisfies the medical requirements isobtained in the tumour volume and a relatively steep drop towards theedge of the irradiation can be achieved. For that to occur, however, aconsiderably smaller beam position spacing and, therewith, considerablymore beam positions than in FIG. 1 have to be planned in FIG. 2, withthe result that the treatment time in FIG. 2 would be many times greaterthan the treatment time in FIG. 1. By means of the present invention,however, the beam width can be varied from beam position to beamposition, so that, as the beam position spacing becomes greater, thebeam profile width can be set wider and, towards the edge, the beamposition spacing can be reduced while simultaneously reducing the beamprofile width.

By means of the apparatus according to the invention, therefore,considerably more homogenised dose distribution can be obtained, as FIG.2 shows, and, at the same time, the number of beam positions periso-section through tumour tissue can be reduced and, towards the edgeof the tumour, the beam position spacing is reduced and simultaneouslythe beam profile width is reduced, as FIG. 3 shows, so that a steep edgedrop and a more precise demarcation from healthy tissue becomespossible.

FIG. 3 shows an illustrative embodiment of a beam position distributionthat becomes possible by employing the apparatus according to theinvention. The apparatus according to the invention allows adaptation ofthe size of an ion beam spot in tumour irradiation with a rasterscanning device composed of raster scanning magnets for raster scanningthe ion beam, with quadrupole magnets determining the size of the ionbeam spot which are arranged directly in front of the raster scanningmagnets, with two magnet power supply units of the quadrupole doublet ofthe quadrupole magnets determining the size of the ion beam spot, theapparatus having a control loop that provides current correction values,by comparing desired and actual values of the prevailing dimension ofthe beam, for two magnet power supply units of the quadrupole doubletarranged directly in front of the raster scanning magnets and that makespossible a defined homogenization and/or a defined variation of the sizeof the ion beam spot during beam extraction and/or from measuring cycleto measuring cycle and/or from beam position to beam position.

FIG. 3 shows for that purpose tumour tissue 1 surrounded by healthytissue 2 and a sharply defined edge 3 which represents the boundarytissue between tumour tissue 1 and healthy tissue 2. Using theabove-mentioned apparatus according to the invention, the beam profilewidth is set wider in the centre 4 of the tumour tissue than in the edgeregion 9 of the tumour tissue 1. In return, a fine beam position rasteris provided in the edge region 9, which is this embodiment has fourtimes the density per unit of area in the edge region 9 compared withthe density per unit of area in the centre 4.

Owing to the regulation of the beam width according to the invention,which acts directly on the quadrupole doublet arranged in front of theraster scanning magnets, both in the horizontal and in the verticaldirection, it is possible, despite the coarse beam position raster inthe centre 4 of the tumour tissue, to obtain a homogenization of thedose distribution and, at the same time, a homogeneous dose distributionalso in the edge region 9 with a considerably more precise demarcationof the edge region of the tumour tissue 1 from the healthy tissue 2 byvirtue of the adaptation of the size of the ion beam spot from beamposition to beam position during the irradiation. That adaptation can becarried out not only from beam position to beam position but also frommeasuring cycle to measuring cycle and, to stabilise the dosedistribution, also during beam extraction. For that purpose, anadditional control loop is provided between a control and read-outmodule and magnet power supply units for horizontal and verticalquadrupoles arranged directly in front of the scanning magnets.

Accordingly, a narrow ion beam spot over a closely spaced beam positionraster is implemented for irradiation of the isoenergy section in theedge region and a large beam spot over a coarse beam position raster inthe centre. Thereby, the total number of beam positions per isoenergycross-section and hence the duration of the irradiation canadvantageously be markedly reduced, and the dose gradient at the edgecan be selected to be very steep when specifying the irradiation plan.

FIG. 4 shows an embodiment of an irradiation system in which theapparatus according to the invention can be employed. The control andmonitoring of the irradiation system is ensured in this case by acomplex electronic system.

The control and monitoring system is composed of three levels, namely asequence control 5, a system control 6 and an operator control 7. Theseoperate independently of one another. Distributed over all three levelsis a safety system 8 which ensures immediate switching-off of the beamin the event of a fault in the system.

The sequence control 5 allows access by the operator control 7 onlyduring initialisation at the start and in the case of emergency stop.During the irradiation, the sequence control 5 operates automatically.In addition to control functions, it also fulfils safety functionswhereby the measured data are compared with the specifications of theirradiation plan and result in the beam being switched off in the eventof deviation above fixed limits.

The system control 6 allows setting of the operating parameters, forexample of the detector voltage. In addition, the system control 6monitors processes that take place “slowly” by reading out a largenumber of system states and switches off the beam where appropriate.

The operator control 7 allows the operator to interact with the controland monitoring system. From the operator control, irradiation plans areloaded into the sequence control 5, irradiations are started, stopped orinterrupted, operator actions and system parameters are logged, theirradiation process and the system state are visualised by reference tomeasurement data and the measured data are archived to produce documentscenarios.

The control and monitoring system is implemented in the form of a VMEenvironment and has operating devices such as input/output devices(terminals) and a computer system consisting of several individualcomputers with the customary peripherals. The devices for monitoring thebeam as to position, width and intensity and the device for requestingand deflecting the beam are coupled to the VME environment via buslines.

The safety system, which operates independently of the sequence control5, monitors the aggregate radiation process for the entire duration ofthe irradiation. It interrupts the irradiation process automatically if,owing to a malfunction, the deflection of the beam is faulty or theparticle number for a point or a layer or the total number of particlesapplied is exceeded. The cause of a malfunction may lie in the actualproduction of the beam or may have its basis in the sequence control 5,the sequence control 5 having, however, auto-monitoring means forinterrupting the irradiation process.

The sequence control 5 has circuit modules (control and read-out modules11-17) which are connected to the operating devices by a common systembus. The system bus is in the form of a VME bus.

Each of the control modules 11 to 17 is connected by a respectiveseparate device bus to a measuring device (such as an ionizationchamber, multiwire chamber etc.) and to an external storage device 27.The device buses are independent of the system bus. The block diagramshown by FIG. 4 accordingly belongs to a control system for an ion beamtherapy unit.

The control system for an ion beam therapy unit accordingly consistsessentially of a technical control room (TKR) in which all of theaccelerator data of the Ethernet are assembled on an acceleratoroperating console and Ethernet router data are passed to the next largerunit of the control system for an ion beam therapy unit of the technicaloperating console in the therapy itself. The central device of thattechnical operating console is the therapy operating computer (TORT)which has a barcode reader (BCL) and which is in communication with theoperating element of the terminals via the therapy Ethernet. Thetechnical operating console in the therapy domain has a medicaloperating console (MBDK) which is in communication with a therapy domain(Cave M) and has a direct connection for triggering beam termination ofthe accelerator. For beam termination, a resonant quadrupole (S021Q1E)for the slow extraction of the beam is zeroed via its power supply unitvia an interlock unit in the bus system of the therapy control system. Adeflecting dipole magnet (TH3MU1) of the beam guide to the therapymeasuring position is likewise zeroed by the interlock unit (ILE) in thebus system (VME) of the therapy control system in order to terminate thebeam or the extraction in the event of a fault.

For the system control (VMESK) per se several microprocessors worktogether on a bus system connection frame (VME crate). In addition tothe data store (ODS) for online display mentioned above and shown inFIG. 4, the system control includes an intensity monitor (IMON) whichco-operates inter alia with an ionization chamber and the read-outelectronics for monitoring the total particle number. In addition, aTrottmann circuit unit (TME) for monitoring the operating ability of theprocessors is present in the system control. In addition to theinterlock unit (ILE) already mentioned and a control bus adapter (KBA),the system control has an analogue/digital module (ADIO) and a systemcontrol computer (SKR) in the bus system (VME) of the system control.

The components of the sequence control (VMEAS) are identical to thecomponents of the data flow diagram shown in FIG. 5, the not shown, thatexclusively fulfils the function of width regulation. The capacity ofthe arrangement shown is entirely adequate, however, for undertaking theadditional task of a width regulation of the ion beam in co-operationwith the magnet power supply units 18 and a control loop between theSAMD, the SAMO1 magnet power supply units 18 of the horizontal andvertical quadrupole magnets 10.

LIST OF REFERENCE NUMERALS

-   1 tumour tissue-   2 healthy tissue-   3 edge of tumour tissue-   4 centre of tumour tissue-   5 sequence control system-   6 system control-   7 operator control-   8 safety system-   9 edge region-   10 quadrupole magnets for horizontal and vertical focusing-   11 control and read-out module SAMI1-   12 control and read-out module SAMI2-   13 control and read-out module SAMP-   14 control and read-out module SAMO1-   15 control and read-out module SAMS-   16 control and read-out module SAMO2-   17 control and read-out module SAMD-   18 magnet power supply units for horizontal and vertical quadrupoles-   19 ion beam-   20 raster scanning magnets-   27 ODS (data store)-   28 SKR (system control computer)-   29 accelerator operating console in TKR-   30 accelerator Ethernet-   31 technical control room, therapy, TKR-   32 Ethernet router-   33 barcode reader, BCL-   34 therapy operating computer, TORT-   35 operating elements, terminals-   36 technical operating console, therapy-   37 medical operater console, therapy-   38 therapy operating computer, TORM-   39 Ethernet bridge-   40 therapy Ethernet-   41 analogue/digital IO module, ADIO-   42 control bus adapter, KBA-   43 interlock unit, ILE-   44 Totmann unit, TME-   45 intensity monitor, IMON-   46 sequence control computer, ASR-   47 digital IO module, DIO-   48 therapy Cave M-   49 separate magnet power supply unit control for terminating beam of    accelerator (S02KQ1E and TH3MU1)-   50 to pulse centre of accelerator, PZA-   51 PET camera-   52 accelerator beam guide into Cave M-   53 patient couch-   54 mini-ridge filter-   55 ionization chamber for intensity monitor-   56 multiwire chamber (multiwire proportional chamber, MWPC)-   57 ionization chamber for intensity measurement (IC)

1. Apparatus for adapting the size of an ion beam spot, having thefollowing features: a raster scanning device composed of raster scanningmagnets (20) for raster scanning the ion beam (19), quadrupole magnets(10) determining the size of the ion beam spot, which quadrupole magnets(10) are arranged directly in front of the raster scanning magnets (20),two magnet power supply units (18) for the quadrupole doublet of thequadrupole magnets (10) determining the size of the ion beam spot, and acontrol loop for providing current correction values, by comparingdesired and actual values of the prevailing dimension of the beam, fortwo magnet power supply units (18) of the quadrupole doublet of thequadrupole magnets (10) determining the size of the ion beam spot, fordefined homogenization and/or for defined variation of the size of theion beam spot during beam extraction and/or from measuring cycle tomeasuring cycle and/or from beam position to beam position, theapparatus having a control and read-out module (SAMD) that controls andreads out a denser ion beam position raster with, at the same time, asmaller ion beam spot size in the edge region (3) than in the volumeregion (4) of a tumour.
 2. Apparatus according to claim 1, wherein theapparatus has a position-sensitive detector (MWPC1) for detecting theion beam width and for producing raw detector data.
 3. Apparatusaccording to claim 1, wherein the apparatus has a plurality of controland read-out modules (SAMO1 and SAMD) and associated data connections inorder to send information on the actual value of ion beam widths to astorage, control and read-out module (SAMD) for storage of themeasurement data.
 4. Apparatus according to claim 1, wherein oneread-out module (SAMD) had a number of free interfaces and a computingcapacity by means of which the tracking of the ion beam width can beperformed.
 5. Apparatus according to claim 1, wherein the apparatus hasa control system that is expanded by one control and read-out module,wherein exclusively the function of ion beam width regulation can beperformed by the additional control and read-out module.
 6. Apparatusaccording to claim 1, wherein the apparatus has a control loop whichstarts from a multiwire ionization chamber (MWPC1) with attached controland read-out module (SAMO1) and leads to a control and read-out module(SAMD) that provides measurement data for graphical representation andactuates two magnet power supply units (18) for horizontal and verticalfocusing of the quadrupole doublet directly in front of the rasterscanning magnets (20).
 7. Method for adapting the size of an ion beamspot in tumour treatment, wherein the method steps: dynamic adaptationof the size of the beam spot in real time by, applying desired valuesfor different ion beam sizes to the quadrupole magnet (10) determiningthe beam size between two successive accelerator cycles or within anacceleration cycle by means of adjustable frequency, obtaining currentcorrection values, by comparing desired and actual values of theprevailing dimension of the beam, for two magnet power supply units (18)of the quadrupole doublet of the quadrupole magnets (10) determining thesize of the ion beam spot, for defined homogenization and/or for definedvariation of the size of the ion beam spot during beam extraction and/orfrom measuring cycle to measuring cycle and/or from beam position tobeam position, irradiating tumour tissue (1) with a denser ion beamposition raster and, at the same time, a smaller ion beam spot size inthe edge region (3) than in the volume region (4) of the tumour. 8.Method according to claim 7, wherein the beam full width at half maximumis adapted to the ion beam position raster in such a way that, in thecase of the fine ion beam position raster in the edge region (3), asmaller beam full width at half maximum is set than in the volume region(4) of the tumour with a coarse ion beam position pattern.
 9. Methodaccording to claim 7, wherein for every measuring cycle real-timesoftware in a control and read-out module (SAMO1) of a multiwireionization chamber (MWPC1) calculates the actual value of the ion beamwidth from the raw detector data of the multiwire ionization chamber(MWPC1).
 10. Method according to claim 7, wherein information on thebeam width is supplied to the module (SAMD) for storing the measurementdata and for controlling and reading-out.
 11. Method according to claim10, wherein, in the module (SAMD) for storing, controlling andreading-out, the actual value of the ion beam spot size is compared inreal time with the information on the desired value of the ion beam spotsize from an irradiation plan.
 12. Method according to claim 7, whereina correction value for magnet power supply units (18) of the quadrupoledoublet of the quadrupole magnets (10) of a high-energy beam guidedirectly in front of the raster scanner, which quadrupole magnets (10)determine the size of the ion beam spot, is determined and set. 13.Method according to claim 7, wherein a correction or resetting isperformed from measuring cycle to measuring cycle of aposition-measuring system or from one ion beam position in theirradiation plan to the next ion beam position.
 14. Method according toclaim 7, wherein setting of the frequency for tracking the ion beamwidth in the form of a parameter of real-time software that determinesthe correction values for the quadrupole doublet is carried out. 15.Method according to claim 14, wherein tracking of the ion beam width isadjustably attenuated.
 16. Method according to claim 15, whereinthreshold values for the ion beam width are established.
 17. Methodaccording to claim 14, wherein threshold values for the ion beam widthare established.